Liquid crystal display device having thin glass substrate on which protective layer formed and method of making the same

ABSTRACT

The LCD according to present invention includes a first substrate and a second substrate, two protective layers including at least one layer formed on outer surface of the first and second substrates, a transparent electrode formed on inner surface of the first substrate or the second substrate, an alignment layer formed on the transparent electrode, and two polarizers attached on the first and second substrates.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a liquid crystal display device,and more particularly to a liquid crystal display device having glasssubstrates uniformly and smoothly formed on its outer surface toincrease the mechanical strength thereof and method of making the same.

[0002] As a display device of a television and a personal computer,etc., a large size cathode ray tube (CRT) display device has been used.However, since the screen must be separated from the electron gun morethan predetermined distance for large size screen CRT, the volume isincreased. Thus, this CRT cannot be applied to the thin weight, smallsize, and low power consumption electronic device such as a wall-mountedtelevision, a portable television and a notebook computer, etc.

[0003] According to the purpose of display device, the flat paneldisplay devices such as LCD (liquid crystal display), PDP (plasmadisplay panel), ELD (electroluminescent display), and VFD (vacuumfluorescent display) have been introduced recently. Among above flatpanel display device, the LCD has been dominantly researched for thegood picture quality and low power consumption. The LCD-applied portabletelevision and notebook computer are on the market resent, but there arealso problems to be solved in this LCD yet. Particularly, the size andweight are important factor of the LCD investigation because of theapparatus have to be in hands of user.

[0004] For small size and light LCD, there are several methods ofreducing the size and weight of the LCD element. However, the drivingcircuit and the thin film transistor, which are necessary element of theLCD, are so thin that the weight cannot be reduced. On the other hand,it is possible to reduce the weight of the glass substrate which is abasic element of the LCD. Specially, since the glass substrate is mostheavy element of the LCD, the method of reducing the weight of the glasssubstrate has been continuously researched.

[0005] The light glass substrate means thin glass substrate. However,the thin glass substrate causes the damage and the surface roughness, sothat the mechanical strength is weakened and the image quality of LCD isdeteriorated.

[0006] In several etching methods of reducing the thickness of the glasssubstrate, it is representative that the substrate is etched in a casewhich was filled with etchant. In this etching method, however, becauseof impurities created in etching process, the substrate is not uniformlyetched.

[0007] Therefore in proposed another etching method, the substrate isetched removing the impurities created in etching process by bubblesthrough a porous plate after a substrate is arranged.

[0008] In this method, however, bubbles appear on the substrate, orcracks occur by mechanical impulse, the bubbles were created in processof manufacturing glass and diameters of several um—several ten um. Incase that the substrate applied to a LCD desirable image quality can notbe achieved because of scattering of the light in a bubble region.Further if the cracks occur on the substrate by an etching process ofthe glass or mechanical impulse, impurities pass into the substrate inmanufacturing process of the LCD thereby a quality of the LCD is down.In addition, since the crack is intensified according to passing oftime, thereby the substrate is brokendown.

[0009] Accordingly in order to decrease weight of the LCD by etching thesubstrate, it is very important to decrease a fault on the substrate aswell as an etching method.

SUMMARY OF THE INVENTION

[0010] An object of the present invention is to provide the LCD havingthin glass substrate which is light and its surface is smooth and strongfrom mechanical impulse.

[0011] In order to achieve this object, the LCD according to presentinvention includes a first substrate and a second substrate, twoprotective layers including at least one layer formed on outer surfaceof the first and second substrates, a transparent electrode formed oninner surface of the first substrate or the second substrate, analignment layer formed on the transparent electrode, and two polarizersattached on the first and second substrates.

[0012] Each the protective layer material may be an inorganic matterhaving a compressive stress or an organic matter having a low viscositycoefficient, further the protective layer may be one layer including aninorganic layer or an organic layer, or a plurality of layers composedof same matter or different matter. The inorganic layer is formed by athin layer depositing method on the substrate, while the organic layeris formed by irradiating the light such as ultraviolet, visible ray,etc., onto a thermosetting resin deposited on the substrate and curingthat.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIGS. 1a, b are drawings showing a glass substrate having aprotective layer in accordance with present invention, FIG. 1arepresents a protective layer on which bubbles appear, FIG. 1brepresents a protective layer on which cracks occur.

[0014]FIG. 2 is a drawing showing a liquid crystal display device havingthe glass substrate of the FIGS. 1a, b.

DETAILED DESCRIPTION OF THE INVENTION

[0015] Reference will now be made in detail to the present preferredembodiments of the invention, examples of which are illustrated in theaccompanying drawings.

[0016]FIGS. 1a, b are drawings showing a glass substrate 1 having theprotective layer, as shown in FIG. 1a, a bubble, which is formed inprocess of manufacturing glass and its diameter is several um—severalten um, is appeared on the thin substrate which is etched less than 0.7mm. Further, since the thickness of the glass substrate 1 is very thin,a crack may be occured by fine mechanical impulse as shown in FIG. 1b.

[0017] A transparent protective layer 8 formed on the substrate 1includes a plurality of layer having an inorganic matter or an organicmatter, or an inorganic matter and an organic matter, then a refractiveindex of each layer is 1.4-1.6. the inorganic layer 8 is formed on thesubstrate 1 by general thin layer deposition method such as sputteringmethod, CVD (chemical vapor deposition) method, and evaporation method.While organic layer 8 is formed by irradiating the light such asultraviolet, visible ray, etc., onto a thermosetting resin deposited onthe substrate and curing that. At this time the inorganic matter havingthe compressive stress and the organic matter having the low viscositycoefficient (about several cp—several ten cp).

[0018] When bubbles appear on the surface of substrate 1 as shown inFIG. 1a, an desirable image quality can not be achived because ofscattering of the light in a bubble region.

[0019] Since the protective layer 8 is formed on the bubble as well asthe surface of substrate 1, diameters of the bubbles are minimized frommicrometer to angstrom. Accordingly when the substrate 1 is applied to aLCD, it is possible to prevent decreasing of an image quality by smallscattering of the light in that region.

[0020] Additionally if cracks occur on the substrate 1 as shown in FIG.1b, the substrate 1 is brokendown slowly according to passing of time inmanufacturing process of the LCD. Further an impurity inserted in thecrack cause to decrease quality of the LCD. While the inorganic layerprevent transmission of the crack by the compressive stress, and thecured organic layer also prevent transmission of the crack, thereby astrong glass substrate for mechanical impulse can be achieved.

[0021] The protective layer 8 may be one layer with an inorganic layeror an organic layer, or a plurality of layers composed of same matter ordifferent matter.

[0022]FIG. 2 is a drawing showing a liquid crystal display device havingtwo glass substrates including the protective layers.

[0023] Each thickness of a first substrate 10 a and a second substrate10 b is less than 0.7 mm, a transparent electrode 12 made of such as ITO(indium tin oxide) is formed on the first substrate. In presentembodiment, although, the transparent electrode 12 is formed on thefirst substrate, it is possible that the transparent electrode 12 isformed on the second substrate. Further alignment layers 13 a, 13 bincluding polyimide or photo alignment material are formed on thetransparent electrode 12, then an alignment direction of the alignmentlayer is determined by using a mechanical or optical method. On theother hand a liquid crystal layer 15 is formed between the first andsecond substrates. The protective layer 18 a, 18 b are an inorganiclayers or an organic layers, or a plurality of layers composed of samematter or different matter and formed on outside surface of both thefirst substrate 10 a and the second substrate 10 b. Continually a firstpolarizer 14 a and a second polarizer 14 b are formed on the protectivelayers 18 a, 18 b.

[0024] Although not showing with drawing, TFTs (thin film transisters)are formed on the first substrate 10 a, and a color filter layer isformed on the second substrate.

[0025] After etching, grinding and scribing two glasses by generaletching method, the protective layers 18 a, 18 b are formed on that, andthe transparent electrode 12 is formed on the protective layer 18 a, 18b by the sputtering method. At this time, also it is possible to makethe substrate 10 a, 10 b after the passivation layers 18 a, 18 b areformed on each the glass. Further the TFTs (not illustrated) are formedon the first substrate 10 a by depositing and photoetching a metallayer, and the alignment layer 13 a, 13 b are formed by mechanicaldepositing or injecting the alignment material. Thereafter a pluralityof spacers (not illustrated) are dispersed to maintain a gap between thefirst and second substrate 10 a, 10 b. After pouring the liquid crystalinto a region between the first and second substrates and the twosubstrates are sealed, and thereby the LCD according to the presentinvention is completed.

[0026] In the above-discussed structure, since the protective layerincludes an inorganic or an organic matter, the thin glass substratethrough etching is bearable from a mechanical impulse.

[0027] Further in etching process, since the inorganic or organic matterhave diameters of the bubbles which a quality of the LCD is down by thatdecreased, it is possible to achieve the good quality LCD having softand uniform surface.

[0028] When cracks occur on the substrate, the protective layer preventtransmission of the crack thereby the substrate is not brokendown.

[0029] As a result, the present invention provides the good quality LCDhaving thin glass substrate light and its surface is smooth and strongfrom mechanical impulse.

[0030] Other embodiments of the invention will be apparent to thoseskilled in the art from consideration of the specification and practiceof the invention disclosed herein. It is intended that the specificationand examples be considered as exemplary only, with a true scope andspirit of the invention being indicated by the following claims.

What is claimed is:
 1. A thin glass substrate of a liquid crystaldisplay device, comprising: a glass; and at least one transparentprotective layer formed on the glass.
 2. The thin glass substrateaccording to claim 1, wherein a refractive index of the protective layeris 1.4-1.6.
 3. The thin glass substrate according to claim 1, whereinthe protective layer is an inorganic layer.
 4. The thin glass substrateaccording to claim 3, wherein the inorganic layer have a compressivestress.
 5. The thin glass substrate according to claim 1, wherein theprotective layer is an organic layer.
 6. The thin glass substrateaccording to claim 5, wherein the organic layer includes a thermosettingresin.
 7. The thin glass substrate according to claim 6, wherein aviscosity coefficient of the thermosetting resin is several cp—severalten cp.
 8. The thin glass substrate according to claim 1, wherein theprotective layer includes one inorganic layer and one organic layer. 9.A liquid crystal display device, comprising: a first substrate and asecond substrate; at least one transparent protective layer formed onouter surface of the first substrate and the second substrate; atransparent electrode formed on inner surface of the first substrate orthe second substrate; an alignment layer formed on the transparentelectrode; and a liquid crystal layer between the first substrate andthe second substrate.
 10. The liquid crystal display device according toclaim 9, wherein a refractive index of the protective layer is 1.4-1.6.11. The liquid crystal display device according to claim 9, wherein theprotective layer is an inorganic layer.
 12. The liquid crystal displaydevice according to claim 11, wherein the inorganic layer has acompressive stress.
 13. The liquid crystal display device according toclaim 9, wherein the protective layer is an organic layer.
 14. Theliquid crystal display device according to claim 13, wherein the organiclayer includes a thermosetting resin.
 15. The liquid crystal displaydevice according to claim 14, wherein a viscosity coefficient of thethermosetting resin is several cp—several ten cp.
 16. The liquid crystaldisplay device according to claim 9, wherein the protective layerincludes at least one inorganic layer and at least one organic layer.17. A method of manufacturing a thin glass substrate of a liquid crystaldisplay device, comprising the steps of: providing a glass; forming asubstrate by processing the glass; and forming a protective layer on theglass substrate.
 18. The method according to claim 17, furthercomprising steps of: grinding a glass; and scribing the ground glass.19. The method according to claim 17, wherein the step of processing theglass is executed after forming the protective layer.
 20. The methodaccording to claim 17, wherein the step of forming the protective layerincludes the step of irradiating the light after depositing an organicmatter on the glass substrate.
 21. The method according to claim 20,wherein the light is an ultraviolet or a visible ray.
 22. The methodaccording to claim 17, wherein the step of forming the protective layerincludes the step of coating an inorganic matter on the glass substrate.23. The method according to claim 17, wherein the step of forming theprotective layer further includes steps of: forming an organic layer bythe light irradiating after depositing an organic matter on the glasssubstrate; and forming an inorganic layer by coating an inorganic matteron the organic layer.
 24. The method according to claim 23, wherein thelight is an ultraviolet or a visible ray.
 25. The method according toclaim 17, wherein the step of forming the protective layer furtherincludes steps of: forming an inorganic layer by coating an inorganic onthe glass substrate; and forming an organic layer by the lightirradiating after depositing an organic matter on the inorganic layer.26. The method according to claim 25, wherein the light is anultraviolet or a visible ray.
 27. A method of manufacturing a liquidcrystal display device, comprising the steps of: providing a firstsubstrate and a second substrate; forming at least one transparentprotective layer on outer surface of the first substrate and the secondsubstrate; forming a transparent electrode on inner surface of the firstsubstrate or the second substrate; forming an alignment layer on thetransparent electrode; and forming a liquid crystal layer between thefirst substrate and the second substrate.